apache/beam · error

error copying file

Error message

error copying file %s: %w

What it means

io.Copy(writer, f) failed while streaming a source file's contents into the zip entry, meaning either reading the source file or (more often) writing to the zip stream failed mid-copy. The error carries the source path; the underlying cause is wrapped from io.Copy.

Solutions

1. Free disk space on the output volume and re-run MakeJar/packJar.
2. Verify the failing file is readable and not corrupt (cmp it against the original JAR entry; re-extract if needed).
3. Check volume quota and filesystem health if the wrapped error is a write error.
4. Retry from a clean state: remove the partial output jar and tmpDir, then re-extract and pack.

if fi, err := os.Stat(path); err != nil || fi.Size() == 0 && expectedSize > 0 { return fmt.Errorf("source file bad: %s", path) }

if _, err = io.Copy(writer, f); err != nil {
    return fmt.Errorf("error copying file %s: %w", path, err)
}
// caller: on ENOSPC/EIO, clean partial jar + tmpDir and retry MakeJar once

When it happens

Trigger: During packJar's walk callback, io.Copy between the opened source file and the zip entry writer errors: source read error (EIO, truncated file) or destination write error (ENOSPC on the volume holding the output jar).

Common situations: Full or failing disk while repacking a large JAR; corrupted/truncated file in the extracted tree; network storage dropping mid-read; quota exceeded on the destination volume.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• error creating jarFile header
• error opening destination file
• error opening source file
• bucket must not be empty
• chunk write failed

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/2ffe2cd6a6c2999e. Report an issue: GitHub.

Appendix: source

Thrown at sdks/go/pkg/beam/core/runtime/xlangx/expansionx/download.go:247

			fileHeader.Method = zip.Deflate
		}

		writer, err := jarFile.CreateHeader(fileHeader)
		if err != nil {
			return fmt.Errorf("error creating jarFile header: %w", err)
		}
		if fileInfo.IsDir() {
			return nil
		}

		f, err := os.Open(path)
		if err != nil {
			return fmt.Errorf("error opening file %s: %w", path, err)
		}
		defer f.Close()

		if _, err = io.Copy(writer, f); err != nil {
			return fmt.Errorf("error copying file %s: %w", path, err)
		}
		return nil
	})
	return err
}

// MakeJar fetches additional classpath JARs and adds it to the classpath of
// main JAR file and compiles a fresh JAR.
func MakeJar(mainJar string, classpath string) (string, error) {
	usr, _ := user.Current()
	cacheDir := filepath.Join(usr.HomeDir, jarCache[2:])

	// fetch jars required in classpath
	classpaths := strings.Split(classpath, " ")
	classpathJars := []string{}
	for _, jar := range classpaths {
		path := expandJar(jar)
		if j, err := getLocalJar(path); err == nil {

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